In the displays of electronic devices such as personal digital assistants (PDAs), laptop computers, office automation (OA) equipment, medical devices, car navigation systems, and the like, touch sensors are provided as an input means. Touch sensors can be classified into a resistive type, an electromagnetic induction type, an optical type, a capacitive type, and the like according to implementation methods thereof.
For example, as shown in FIG. 1, a capacitive-type touch sensor can be divided into a display region and a non-display region according to whether visual information is displayed.
The display region is intended to display an image provided by a device combined with the touch sensor, and also to sense a touch signal input by a user in a capacitive manner. In the display region, an electrode pattern layer 40 (also referred to as a touch sensor layer) including a plurality of electrode patterns 41 and 42 formed in directions crossing each other is formed.
Meanwhile, in the non-display region lying outside the display region, a connection line portion 20 (also referred to as a trace portion) electrically connected to the electrode pattern layer 40 and a pad portion 30 electrically connected to the connection line portion 20 are formed.
In the touch sensor having the above-described configuration, indium tin oxide (ITO) is generally used in the electrode patterns 41 and 42 constituting the electrode pattern layer 40. It is known that ITO applied to a touch sensor easily cracks on a flexible substrate and has a sheet resistance of about 200 Ω/square (sq) or about 100 Ω/sq according to the product.
Sheet resistance of ITO can be adjusted according to a thickness thereof. To implement a touch sensor that has a high resolution and a small thickness, it is necessary to minimize sheet resistance. However, a reduction in sheet resistance results in a relative increase in the thickness of ITO, thus limiting a reduction in the thickness of a product. Also, when the thickness of ITO increases, transmittance is degraded, and the visibility of a film is degraded. Therefore, it is necessary to develop a new touch sensor fabrication method for reducing sheet resistance of an electrode pattern layer without increasing an ITO thickness, and thereby causing a touch sensor to have a high resolution, a large area, and a small thickness.
Further, when a touch sensor is fabricated by attaching a film layer on a substrate, the film layer may be deformed due to a high-temperature process, and a solution to this problem is necessary.